This invention relates to the field of information processing, and more particularly, to the matching of values in information systems.
Information processing applications must often find a value within a range of values. For example, a sorting system may organize discrete units of information into groups defined by numerical boundaries. Before assigning each discrete unit of information to a group, the relationship between each discrete unit of information and the numerical boundaries must be established. Defining these relationships often requires finding a value within a range of values. In some sorting systems, this is accomplished using a compute intensive sort algorithm in combination with a high performance microprocessor. Unfortunately, high performance microprocessors are expensive, and therefore not suitable for use in products directed to the consumer market.
An analog-to-digital (A/D) converter generates digital output information related to analog input information. The conversion process associated with one type of A/D converter requires manipulating discrete pieces of information, the on and off states of resistor ladder switches, in such a way that the final configuration of resistor ladder switches matches a value within a range of values. Modem A/D converters are designed to operate on a single chip and to function in a variety of end user applications, such as cellular telephones and video games. A single A/D converter design may be required to function in an application that requires eight, twelve, sixteen or more bits of resolution. Designers attempt to provide this flexibility in an A/D converter by providing an on chip microprocessor. Unfortunately, the supplied microprocessor often has a limited instruction set, and operates at a low frequency, so the requirements for applications that must operate at both high frequency and high resolution, such as quickly matching a two byte value within a range of values, are difficult to meet.
Some control systems seek to drive a difference signal, which is the difference between an output information signal and an input signal, to zero in order to maintain a constant relationship between the input signal and the output information signal. This process of driving the difference signal to zero may require the identification of a value within a range of values.
In modern digital control systems, the control function is often performed by a microprocessor. In some systems designed primarily for high reliability, such as systems designed for use in satellites, high function may also be required. High function microprocessors tend to fail more often than low function microprocessors, so it is difficult to meet both requirements, and often a low function microprocessor is selected for a particular application. Unfortunately, the same algorithms and software that accomplish tasks on a high function microprocessor, such as identifying a value within a range of values, do not work on low function microprocessors.
For these and other reasons there is a need for the present invention.
The above-mentioned problems and other problems are addressed by the present invention and will be understood by one skilled in the art upon reading and studying the following specification. A method of finding an unknown value from within a range of values is disclosed that divides the range into weighted subranges and then, beginning with an arbitrary search value within the range, performs a number of simple comparisons to determine the value for each subrange that will result in a match with the target value. This method can also detect those cases where the target value lies outside the range.
In one embodiment, the method of finding an unknown value within a range of values is applied to impedance matching. In this embodiment, the output impedance of a pin on an integrated circuit is automatically matched to the impedance of the load connected to it. The output driver has a controllable impedance that can be adjusted within a specific range of impedances to match the external load impedance it is to drive.